For operations off normally passable roads, e.g. for performing soil sounding operations and the like, off-road vehicles are being used with plural wheeldrive and special off-road transmissions. In order to obtain a dependable drive, generally three-axle vehicles with double rear axles are being used, and, moreover, special transmissions with a high deceleration and differential blocking are utilized.
For transport on the road, however, generally a two-axle vehicle will be sufficient. It is an object of the invention to provide such a vehicle which is also suitable for off-road operations. The motor vehicle according to the invention can be obtained, in particular, by a suitable adaptation of a current two-axle vehicle, and has the characteristics mentioned in the characterizing portion of claim 1.
In this manner a normal motor vehicle can be made suitable, for being used as an off-road vehicle. As known continuous tracks are very efficient for this purpose. Since, for the envisaged purposes, the driving speeds off-road are relatively low, e.g. not more than about 5 km/h, such a track drive can, therefore, be constructed in a rather simple way since no spring suspension is required.
In particular the drive of the auxiliary frame provided with continuous tracks can be coupled with the shift means of the transmission, so that the track drive will be automatically switched on and off as soon as the auxiliary frame is lowered or retracted respectively.
If the vehicle should be horizontally positioned during operations, e.g. in the case of soil sounding or soil drilling operations, the driving means for the auxiliary frame can be used for positioning the vehicle horizontally when the caterpillar tracks have been lowered.